Biology

Castform is an artificial Pokémon that changes appearance and attitude based on the weather. Its body is made of cells exactly like those of water molecules, causing its cellular structure to be altered by temperature and humidity. It uses this ability to protect its tiny body. In its Normal Form, it resembles a plain, gray cloud with a single wisp extending from the top of its head. When in its Sunny Form, its lower half becomes pure white, while the head turns orange has develops small orange spheres around it. This gives it the overall appearance of the sun above a small cloud. While in its Rain Form, it will have a dark gray lower half resembling a storm cloud. The head will be blue and resemble a raindrop. In its Snowy Form, its head turns purplish-blue. The rest of the body changes into the shape of a mint green, cumulonimbus cloud. Regardless of the form it takes, it will always have a large, spherical head and a lighter colored mask-like marking over its eyes. Aside from its various forms, Castform is able to utilize weather powers in the form of its previously signature move, Weather Ball. Despite its manmade origins, it can be found in grassland areas.

In the manga

In the Pokémon Adventures manga

A Castform, nicknamed Fofo, belongs to Ruby and first appeared in Lombre Larceny. Previously, she belonged to Mr. Stone, who was injured in an attack by Team Aqua. Fofo was then given to Gabby and Ty to be cared for while he was being healed. She later decided to travel with Ruby when he began traveling with the reporters because she was lonely. Until he was reunited with Rara, Fofo was Ruby's go to Smart Contest Pokémon.

Origin

Castform resembles a living cloud and acts like weather in general, but it may also be based on a weather balloon. It is similar in both concept and design to a teru teru bōzu, a Japanese charm doll used to wish for good weather. Its forms and their types may have originated from the English saying "rain, hail, or shine." As Castform is said to be composed of molecules similar to water, its shape of a large sphere with two smaller orbs resembles an H2O molecule.

Name origin

Castform may be a combination of forecast (the prediction of weather) and transform or form (referring to its ability to change form depending on the weather). The German and French names reflect this.

Powalen may be a combination of ポワン powan (onomatopoeia of a sudden transformation, similar to "poof" in English) and 変わる kawaru (to change or transform).